Kit for carrying out chemically induced fluorescence immunoassay

ABSTRACT

A competitive protein binding method is provided for the determination of an analyte which is a member of an immunological pair consisting of ligand and receptor for the ligand. A chemiluminescent source is employed comprised of one or more individual members, one chemiluminescent source member being conjugated to one of the members of the immunological pair, so as to provide chemiluminescence adjacent to the site of conjugation. A quencher molecule is conjugated to a member of the immunological pair. When the members of the immunological pair bind, the quencher molecule is brought within quenching distance of the chemiluminescent source so as to inhibit the emission of light by the chemiluminescent source. The amount of analyte present in the assay medium affects the amount of binding between the members of the immunological pair which results in quenching of the chemiluminescence. By observing the light emitted from the assay medium, either from the chemiluminescent source or the quencher, the change in light emission in relation to the concentration of analyte present in the assay medium can be used to determine the amount of analyte present in the assay medium. By employing standards having known amounts of analyte, the amount of analyte in an unknown sample can be quantitatively determined. 
     Reagent kits can be provided having predetermined amounts of the reagents, so as to substantially optimize the sensitivity of the assay.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of application Ser. No. 893,910, filed Apr. 5,1978 now U.S. Pat. No. 4,220,450.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The clinical diagnostic field has seen a broad expansion in recentyears, both as to the variety of materials which may be readily andaccurately determined, as well as the methods for the determination. Onebroad category of techniques involves the use of an organic receptorwhich is able to specifically bind to a particular spatial and polarorganization of another molecule. For the most part, these compounds areantibodies, which are able to distinguish between the compound orcomposition of interest, and other compounds of analogous structure. Byvirtue of the binding of the receptor to a labeled ligand, one is ableto distinguish between labeled ligand which is bound to receptor andunbound labeled ligand.

The observed effect of binding by the receptor will depend upon thelabel. In some instances, the binding of the antibody merely providesfor a differentiation in molecular weight between bound and unboundlabeled ligand. In other instances, the presence of the receptor mayaffect the nature of the signal obtained from the label, so that thesignal varies with the amount of receptor bound to labeled ligand. Afurther variation is that the receptor is labeled and the ligandunlabeled. Where receptors are labeled with two different labels whichinteract when in close proximity, the amount of ligand present affectsthe degree to which the labels on the receptor may interact.

In developing an assay, there are many considerations. One considerationis the signal response to changes in the concentration of analyte. Asecond consideration is the ease with which the protocol for the assaymay be carried out. A third consideration is the variation ininterference from sample to sample. Ease of preparation and purificationof reagents, availability of equipment, ease of automation, andinteraction with ligands, are additional considerations, which do notexhaust the various concerns in developing a useful assay.

There is therefore a continuing need for new and accurate techniqueswhich can be adapted for a wide spectrum of different ligands or be usedin specific cases where other methods may not be readily adaptable.

2. Brief Description of the Prior Art

U.S. Pat. No. 3,709,868 is exemplary of a radioimmunoassay. U.S. Pat.No. 3,960,834 is exemplary of a spin immunoassay. U.S. Pat. No.3,654,090 and German Auslegungsschrift No. 2,223,385 are exemplary ofenzyme immunoassays. Articles of interest include an article by LudwigBrand and James R. Gohlke, Annual Review of Biochemistry, 41, 843-868(1972) and Stryer, Science, 162, 526 (1968). Smith, FEBS Letters 77, 25,(1977) describes a fluorescent immunoassay, where thyroxine is bound toa fluorescer and quenches the fluorescer, the quenching being reversedby binding of antibody to thyroxine. See also, Ullman et al, J. Biol.Chem. 251, 4172 (1976).

An excellent review of chemiluminescence may be found in McCapra,Quarterly Reviews 20, 485 (1966).

SUMMARY OF THE INVENTION

A competitive protein binding assay is provided having as an analyte amember of an immunological pair which consists of ligand and receptorfor the ligand. The assay is predicated on the presence of the analytein an assay medium affecting the degree to which a chemiluminescencesource is quenched by energy transfer to a quencher, at relatively longdistances. By conjugating the chemiluminescence source or where thechemiluminescence source requires a plurality of components, onecomponent of the chemiluminescence source, with a member of theimmunological pair and conjugating a quencher with a member of theimmunological pair, reagents can be prepared which when combined in theassay medium will provide varying degrees of light emission, dependingupon the amount of analyte present in the assay medium.

In particular, the chemiluminescence source or component thereof and thequencher may be conjugated to either the ligand or the receptor and theresulting reagent combined in an aqueous, normally buffered medium at amild temperature, and the amount of light emitted determined. Bycomparison with assay media having known amounts of analyte, aquantitative relationship can be developed between the quanta of emittedlight and the amount of analyte in the assay medium.

Kits can be provided, where the reagents are included in premeasuredamounts, so that they may be used directly or may be readily diluted toassay reagent solutions to provide concentrations which substantiallyoptimize the sensitivity and performance of the assay.

DESCRIPTION OF THE SPECIFIC EMBODIMENTS

In accordance with the subject invention, chemiluminescence is employedto provide a signal related to the amount of analyte in an assay medium.The analyte is a member of an immunological pair which includes ligandand receptor. By conjugating the chemiluminescence source or where thesource is comprised of more than one component, one component of thechemiluminescence source, with a member of the immunological pair and aquencher with a member of the immunological pair, the presence ofanalyte affects the amount of quencher which is within quenchingdistance of the conjugated chemiluminescence source. By combining thechemiluminescence source reagent and the quencher reagent where the twolabels are on different molecules, and additional immunological pairmembers, as required, with the analyte in an assay medium, including anyancillary reagents necessary for the chemiluminescence, and determiningthe amount of light emitted from the assay medium, at a particularwavelength or a range of wavelengths from the assay medium, in relationto an assay medium having a known amount of analyte, the amount ofanalyte in the sample can be determined.

The method is predicated on the observation that when a dye is within alimited distance from a chemiluminescer in the excited state, thechemiluminescer may transfer its energy to the quencher withoutcollision and without emitting radiation. The quencher may then emitradiation of a higher wavelength than the chemiluminescer or may losethe energy by radiationless decay. One can conjugate the member of thechemiluminescence source and the quencher to either ligand or receptor,so that when the two conjugates are brought together the amount ofquencher within quenching distance of the chemiluminescer is affected bythe amount of analyte present in the assay medium. The nature and amountof light emitted from the assay medium will therefore be a function ofthe analyte present in the assay medium. By performing assays with knownamounts of analyte, one can develop a quantative relationship betweenthe amount of analyte in the assay medium and the amount of radiationemitted from the assay medium at one or more wavelengths.

Definitions

Analyte--the compound or composition to be measured, which may be aligand which is mono- or polyepitopic, antigenic or haptenic, a singleor plurality of compounds which share at least one common epitopic siteor a receptor.

Ligand--any compound for which a receptor naturally exists or can beprepared.

Ligand analog--a modified ligand which can compete with the analogousligand for receptor, the modification providing means to join to a labelor to a hub nucleus.

Poly(ligand analog)--a plurality of ligand analogs joined togetherconvalently, normally to a hub nucleus, to provide a compound having aplurality of epitopic sites capable of competing with the analogousligand for receptor.

Label--either a component of a chemiluminescence source or a quencherdye, which form a light emitting reciprocal pair, where the quencher dyehas a high transition probability of absorbing energy from thechemiluminescence source.

(a) chemiluminescer label--a compound which by itself or in combinationwith other compounds produces a molecule in an electronically excitedstate, which molecule can decay to a lower energy state by the emissionof light and the total process results in a chemical change in one ormore of the compounds.

(b) quencher--a molecule capable of inhibiting the chemiluminescentemission of light, when within a short but non-colliding distance,usually less than about 100 A, of the chemiluminescer molecule, byaccepting the energy which would otherwise be emitted aschemiluminescent light. In effect, the quencher need not be the nearestneighbor to the chemiluminescer to effect quenching.

Label-conjugate--the label, either a compound of the chemiluminescencesource or the quencher, is bonded, either by a bond or linking chain, toa member of the immunological pair but not both to the same molecule.The conjugate will have at least one label and may have a plurality oflabels bonded to the member of the immunological pair or a plurality ofsuch members bonded to the label or a plurality of ligands and labelsi.e. poly(ligand analog)-polylabel. In particular, where an enzyme isthe component of the chemiluminescence source employed as the label, aplurality of ligand analogs may be conjugated to the enzyme to form apoly(ligand analog) label.

Receptor--any compound or composition capable of recognizing aparticular spatial and polar organization of a molecule i.e. epitopicsite. Illustrative receptors include naturally occurring receptors,antibodies, enzymes, lectins, Fab fragments and the like. The receptormay be monovalent or polyvalent in receptor sites usually polyvalente.g. antibodies. For any specific ligand, the receptor will be referredto as "antiligand". The receptor-antiligand-and its reciprocal ligandform an immunological pair.

Poly(ligand analog)-label--a composition in which a plurality of ligandanalogs and one or a plurality of labels are bonded together whereby theligand analog and label are in juxtaposition, so that when receptor isbound to ligand analog, label on the labeled receptor is in withinquenching distance of the reciprocal label. Where an enzyme is part ofthe chemiluminescence source and the ligand is haptenic, a plurality ofligand analogs may be bonded to the enzyme. Alternatively, a pluralityof ligand analogs and one or more labels may be conjugated to a watersoluble polyfunctionalized hub nucleus.

Assay

The subject assay is carried out in an aqueous, normally homogeneous,zone normally, but not necessarily at a moderate pH, generally close tooptimum assay sensitivity. The assay zone for the determination ofanalyte is prepared by employing in an appropriate assay solution,usually buffered, the unknown sample, which may have been subject toprior treatment, the chemiluminescer labeled reagent and the quencherlabeled reagent (includes poly(ligand analog)-polylabel), and asappropriate ligand or antiligand.

The presence of antiligand or ligand in combination with a predeterminedamount of antiligand in the assay medium controls the degree to whichthe quencher comes within quenching distance of the chemiluminescer.

There are four basic variations in the preparation of the quencher andchemiluminescer reagents. The four variations are:

(1) chemiluminescer conjugated to ligand as chemiluminescer labeledligand and quencher conjugated to receptor as quencher labeledantiligand;

(2) quencher conjugated to ligand as quencher labeled ligand andchemiluminescer conjugated to receptor as chemiluminescer labeledantiligand; and

(3) chemiluminescer conjugated to receptor as chemiluminescer labeledantiligand and quencher conjugated to receptor as quencher labeledantiligand.

(4) chemiluminescer conjugated to ligand as chemiluminescer labeledligand and quencher conjugated to ligand as quencher labeled ligand.

With the first two combinations, when the reagents are combined, thequencher will be in quenching distance of the chemiluminescer. Thepresence of analyte, either ligand or antiligand, will serve to reducethe amount of energy transfer between the chemiluminescer and quencherby diminishing the number of quencher molecules within quenchingdistance of the chemiluminescer. In the third combination, apolyepitopic ligand (includes poly(ligand analog)) must be added foreither antiligand or monoepitopic ligand as analyte. Where the ligand ispolyepitopic, increased quenching will be observed as the concentrationof the polyepitopic ligand increases to a maximum quenching, followed bydecreased quenching as the concentration of polyepitopic ligandcontinues to increase. Thus, a biphasic response is obtained, so thatone must know on which portion of the curve one is operating in order toobtain a discrete result. By contrast, with poly(ligand analog), thepresence of monoepitopic ligand will serve to diminish quenching. Withreceptor as analyte, increasing concentrations of receptor will alsoserve to diminish quenching.

Where the chemiluminescer and the quencher are both conjugated toligand, an assay for either ligand or polyvalent antiligand may beperformed. Where the assay is for ligand, the two label-conjugates areemployed in conjunction with antiligand which brings the chemiluminescerand quencher together into quenching distance of each other. Theaddition of ligand reduces the amount of chemiluminescer and label whichare within quenching distance. For the determination of antiligand thetwo label-conjugates are employed. With increasing amounts ofantiligand, there will be a decrease of chemiluminescence to a minimumand then an increase as the concentration of antiligand increases. Ifone is uncertain as to which portion of the biphasic curve is involved,one or more sample dilutions will indicate the particular concentration.

It should be understood, that in referring to quenching, all that isintended is that there be transfer of energy from the chemiluminescer tothe quencher. The result of this transfer will be that light of a singleor range of wavelengths which might otherwise have been emitted by thechemiluminescer will be transferred to the quencher, which may thenfluoresce, emitting light of a higher wavelength than the energyabsorbed. Depending upon the quantum efficiency of emission of thechemiluminescer, the efficiency of energy transfer from thechemiluminescer to the quencher, and the quantum efficiency of emissionof the quencher, as well as the wavelength range which is monitored, onemay observe greater or lesser amounts of light due to the quenching.Therefore, when referring to quenching, it is not intended that therenecessarily be a diminution of the signal which is observed. In fact, ifone is observing the light emitted by the quencher, increasing quenchingwill result in an increasingly large signal.

A special situation exists with small haptens, those of from about 125to 2000 molecular weight. With these haptens a substantially reducedchemiluminescence can be achieved i.e. quenching without quencher bondedto receptor, particularly where the receptor is an antibody. While thereduction in signal will not be as great as when quencher is conjugatedto receptor, a sufficient reduction may be achieved to have anacceptable assay. Except for using receptor without quencher, the assaywill be performed in the same manner, reading the light emitted by thechemiluminescer.

In carrying out the assay, an aqueous medium will normally be employed.Other polar solvents may also be employed, usually oxygenated organicsolvents of from one to six, more usually from one to four carbon atoms,including alcohols, ethers and the like. Usually, these cosolvents willbe present in less than about 40 weight percent, more usually in lessthan about 20 weight percent.

The pH for the medium will usually be in the range from about 5 to 12,more usually in the range from about 7 to 10, and when enzymes areemployed as part of the chemiluminescence source, 7 to 9. Variousbuffers may be used to achieve the desired pH and maintain the pH duringthe determination. Illustrative buffers include borate, phosphate,carbonate, Tris, barbital and the like. The particular buffer employedis not critical to this invention, but in individual assays, one buffermay be preferred over another.

Moderate temperatures are normally employed for carrying out the assayand usually constant temperatures during the period of the assay will beemployed. The temperatures will normally range from about 10° to 50° C.,more usually from about 15° to 40° C.

The concentration of analyte which may be assayed will generally varyfrom about 10⁻⁴ to 10⁻¹⁵ M, more usually from about 10⁻⁶ to 10⁻¹³ M.Stated another way, the concentration ranges of interest will generallybe from about 10⁻³ to 10⁻¹⁴ g/ml.

In addition to the concentration range of analyte of interest,considerations such as whether the assay is qualitative, semi-quantativeor quantitative, the equipment employed, and the characteristics of thereagents will normally determine the concentration of the reagents.While the concentration of analyte will determine the range ofconcentrations of the other reagents, normally to optimize thesensitivity of the assay, individual reagent concentrations will bedetermined empirically. Since the binding constant and binding profileof receptors will vary, for example, with antibodies from bleed tobleed, each new batch of antibodies may require different concentrationratios for the different reagents.

Normally, for mono- and polyepitopic ligand analytes, the concentrationof antiligand based on binding sites will be about equal to the minimumconcentration of interest based on binding sites and not more than about50 times the maximum concentration of interest based on binding sites,usually about 1 to 10 times, and more usually about 1 to 3, times themaximum concentration of interest based on binding sites.

For polyepitopic ligand receptor analytes, the equivalent ratios oflabeled ligand or ligand to receptor analyte will generally be in therange of about 0.01 times the minimum concentration of interest and notmore than about 100 times the maximum concentration of interest based onbinding sites. The labeled receptor employed in conjunction with thelabeled ligand or ligand will generally be present in from about 0.01 to100 times the concentration of ligand or labeled ligand based on bindingsites.

For polyepitopic ligand analytes, where labeled ligand is employed, theconcentration of labeled ligand will generally be not less than about10⁻⁴, more usually not less than about 10⁻² times the minimumconcentration of interest and usually in the range of about equal to theminimum concentration of interest and not exceeding about the maximumconcentration of interest. The ratio of labeled receptor will generallybe not less than about 0.1 times the concentration of labeled ligandbased on binding sites and not greater than about 100 times theconcentration of labeled ligand based on binding sites.

For monoepitopic ligand analytes and monoepitopic ligand receptoranalytes, when employing labeled ligand (includes poly(ligandanalog)-label), the concentration of labeled ligand based on bindingsites will usually be not less than 10⁻⁴ times the minimum concentrationof interest, more usually not less than 10⁻² times the minimumconcentration of interest and usually in the range of about the minimumconcentration of interest to the maximum concentration of interest. Whenpoly(ligand analog) is employed with labeled antiligand, theconcentration of poly(ligand analog) will fall within the same ranges asindicated for the labeled ligand and the concentration of antiligand hasbeen indicated previously.

The order of addition of the various reagents may vary widely, dependingupon whether an equilibrium or rate measurement is involved, the natureof the reagents, the rate at which equilibrium is achieved between theligand and antiligand, and the nature of the chemiluminescence source.Where the chemiluminescence source has a plurality of components, withone of the components being a label, the chemiluminescence can beinitiated at any time by the addition of the other components of thechemiluminescence source. In those situations where thechemiluminescence source involves more than one component, the labeledreagents and the unknown may be combined simultaneously, followed by theaddition of the other components of the chemiluminescence source.Alternatively, one could combine the analyte with the labeledantiligand, followed by the addition of labeled ligand, as appropriate,followed by the addition of the remaining components of thechemiluminescence source. The various additions may be interrupted byincubation. In those instances where the chemiluminescence source is asingle component, normally the labeled receptor will be combined withthe analyte, followed by the addition of the labeled ligand, asappropriate.

Depending on the mode employed, equilibrium or nonequilibrium, the rateof binding of the antiligand to ligand and labeled ligand and therelative concentrations of the ligand, labeled ligand and labeledantiligand, one or more incubation steps may be involved. Normally,times between additions may vary from a few seconds to many hours,usually not exceeding 16 hrs, more usually not exceeding 6 hrs. Usually,incubation times will vary from about 0.5 min to 1 hr, more usually fromabout 0.15 min to 30 min. Since the ultimate result will be dependentupon the result obtained with standard(s) treated in substantially thesame manner, and when possible in the identical manner the particularmode and periods of time are not critical, so long as significantreproducible differentiations are obtained with varying concentrationsof analyte.

Depending upon the choice of assay protocol, the equipment employed andthe concentration of analyte involved, assay volumes may be as small asabout 1 μl, more usually being about 25 μl, and will usually not exceed5 ml, more usually not exceeding 2 ml.

The assay measurement will depend upon counting the quanta of lightemitted from the assay medium. Various instruments may be used, such asscintillation counters, photocells or the like, which are capable ofmeasuring light at a single or over a range of wavelengths.

Materials

The primary components in the subject assay for analyte, which may ormay not be employed in every case are: labeled ligand (includespoly(ligand analog)-label); labeled antiligand; ligand; antiligand; andadditional components as required for the chemilumiinescence source.

Analyte

The ligand analytes of this invention are characterized by beingmonoepitopic or polyepitopic. The polyepitopic ligand analytes willnormally be poly(amino acids) i.e. polypeptides and proteins,polysaccharides, nucleic acids, and combinations thereof. Suchcombinations of assemblages include bacteria, viruses, chromosomes,genes, mitochondria, nuclei, cell membranes, and the like.

For the most part, the polyepitopic ligand analytes employed in thesubject invention will have a molecular weight of at least about 5,000,more usually at least about 10,000. In the poly(amino acid) category,the poly(amino acids) of interest will generally be from about 5,000 to5,000,000 molecular weight, more usually from about 20,000 to 1,000,000molecular weight; among the hormones of interest, the molecular weightswill usually range from about 5,000 to 60,000 molecular weight.

The wide variety of proteins may be considered as to the family ofproteins having similar structural features, proteins having particularbiological functions, proteins related to specific microorganisms,particularly disease causing microorganisms, etc.

The following are classes of proteins related by structure:

protamines

histones

albumins

globulins

scleroproteins

phosphoproteins

mucoproteins

chromoproteins

lipoproteins

nucleoproteins

glycoproteins

unclassified proteins, e.g. somatotropin, prolactin, insulin, pepsin

A number of proteins found in the human plasma are important clinicallyand include:

Prealbumin

Albumin

α₁ -Lipoprotein

α₁ -Acid glycoprotein

α₁ -Antitrypsin

α₁ -Glycoprotein

Transcortin

4.6S-Postalbumin

Tryptophan-poor

α₁ -glycoprotein

α₁ χ-Glycoprotein

Thyroxin-binding globulin

Inter-α-trypsin-inhibitor

Gc-globulin

(Gc 1-1)

Gc 2-1)

(Gc 2-2)

Haptoglobin

(Hp 1-1)

(Hp 2-1)

(Hp 2-2)

Ceruloplasmin

Cholinesterase

α₂ -Lipoprotein(s)

α₂ -Macroglobulin

α₂ -HS-glycoprotein

Zn-α₂ -glycoprotein

α₂ -Neuramino-glycoprotein

Erythropoietin

β-lipoprotein

Transferrin

Hemopexin

Fibrinogen

Plasminogen

β₂ -glycoprotein I

β₂ -glycoprotein II

Immunoglobulin G

(IgG) or γG-globulin

Mol. formula:

γ₂ κ₂ or γ₂ λ₂

Immunoglobulin A (IgA)

or γA-globulin

Mol. formula:

(α₂ κ₂)^(n) or (α₂ λ₂)^(n)

Immunoglobulin M

(IgM) or γM-globulin

Mol. formula:

(μ₂ κ₂)⁵ or (μ₂ λ₂)⁵

Immunoglobulin D (IgD)

or γD-Globulin (γD)

Mol. formula:

(δ₂ κ₂) or (δ₂ λ₂)

Immunoglobulin E (IgE)

or γE-Globulin (γE)

Mol. formula:

(ε₂ κ₂) or (ε₂ λ₂)

Free K and γ light chains

Complement factors:

C'1

C'1q

C'1r

C'1s

C'2

C'3

β₁ A

α₂ D

C'4

C'5

C'6

C'7

C'8

C'9

Important blood clotting factors include:

    ______________________________________                                        BLOOD CLOTTING FACTORS                                                        International designation                                                                      Name                                                         ______________________________________                                        I                Fibrinogen                                                   II               Prothrombin                                                  IIa              Thrombin                                                     III              Tissue thromboplastin                                        V and VI         Proaccelerin, accelerator                                                     globulin                                                     VII              Proconvertin                                                 VIII             Antihemophilic globulin (AHG)                                IX               Christmas factor,                                                             plasma thromboplastin                                                         component (PTC)                                              X                Stuart-Prower factor,                                                         autoprothrombin III                                          XI               Plasma thromboplastin                                                         antecedent (PTA)                                             XII              Hagemann factor                                              XIII             Fibrin-stabilizing factor                                    ______________________________________                                    

Important protein hormones include:

Peptide and Protein Hormones

Parathyroid hormone

(parathromone)

Thyrocalcitonin

Insulin

Glucagon

Relaxin

Erythropoietin

Melanotropin

(melanocyte-stimulating

hormone; intermedin)

Somatotropin

(growth hormone)

Corticotropin

(adrenocorticotropic hormone)

Thyrotropin

Follicle-stimulating hormone

Luteinizing hormone

(interstitial cell-stimulating hormone)

Luteomammotropic hormone

(luteotropin, prolactin)

Gonadotropin

(chorionic gonadotropin)

Tissue Hormones

Secretin

Gastrin

Angiotensin I and II

Bradykinin

Human placental lactogen

Peptide Hormones from the Neurohypophysis

Oxytocin

Vasopressin

Releasing factors (RF)

CRF, LRF, TRF, Somatotropin-RF,

GRF, FSH-RF, PIF, MIF

Other polymeric materials of interest are mucopolysaccharides andpolysaccharides.

Illustrative antigenic polysaccharides derived from microorganisms areas follows:

    ______________________________________                                        Species of Microorganisms                                                                       Hemosensitin Found in                                       ______________________________________                                        Streptococcus pyogenes                                                                          Polysaccharide                                              Diplococcus pneumoniae                                                                          Polysaccharide                                              Neisseria meningitidis                                                                          Polysaccharide                                              Neisseria gonorrhoeae                                                                           Polysaccharide                                              Corynebacterium diphtheriae                                                                     Polysaccharide                                              Actinobacillus mallei;                                                                          Crude extract                                               Actinobacillus whitemori                                                      Francisella tularensis                                                                          Lipopolysaccharide                                                            Polysaccharide                                              Pasteurella pestis                                                            Pasteurella pestis                                                                              Polysaccharide                                              Pasteurella multocida                                                                           Capsular antigen                                            Brucella abortus  Crude extract                                               Haemophilus influenzae                                                                          Polysaccharide                                              Haemophilus pertussis                                                                           Crude                                                       Treponema reiteri Polysaccharide                                              Veillonella       Lipopolysaccharide                                          Eryipelothrix     Polysaccharide                                              Listeria monocytogenes                                                                          Polysaccharide                                              Chromobacterium   Lipopolysaccharide                                          Mycobacterium tuberculosis                                                                      Saline extract of 90%                                                         phenol extracted                                                              mycobacteria and poly-                                                        saccharide fraction of                                                        cells and tuberculin                                        Klebsiella aerogenes                                                                            Polysaccharide                                              Klebsiella cloacae                                                                              Polysaccharide                                              Salmonella typhosa                                                                              Lipopolysaccharide,                                                           Polysaccharide                                              Salmonella typhi-murium;                                                                        Polysaccharide                                              Salmonella derby                                                              Salmonella pullorum                                                           Shigella dysenteriae                                                                            Polysaccharide                                              Shigella flexneri                                                             Shigella sonnei   Crude, polysaccharide                                       Rickettsiae       Crude extract                                               Candida albicans  Polysaccharide                                              Entamoeba histolytica                                                                           Crude extract                                               ______________________________________                                    

The microorganisms which are assayed may be intact, lysed, ground orotherwise fragmented, and the resulting composition or portion, e.g. byextraction, assayed. Microorganisms of interest include:

Corynebacteria

Corynebacterium diptheriae

Pneumococci

Diplococcus pneumoniae

Streptococci

Streptococcus pyogenes

Streptococcus salivarus

Staphylococci

Staphylococcus aureus

Staphylococcus albus

Neisseriae

Neisseria meningitidis

Neisseria gonorrheae

    ______________________________________                                        Enterobacteriaciae                                                            Escherichia coli                                                              Aerobacter aerogenes     The coliform bacteria                                Klebsiella pneumoniae                                                         Salmonella typhosa                                                            Salmonella choleraesuis  The Salmonellae                                      Salmonella typhimurium                                                        Shigella dysenteriae                                                          Shigella schmitzii                                                            Shigella arabinotarda                                                         Shigella flexneri        The Shigellae                                        Shigella boydii                                                               Shigella Sonnei                                                               Other enteric bacilli                                                         Proteus vulgaris                                                              Proteus mirabilis        Proteus species                                      Proteus morgani                                                               Pseuomonas aeruginosa                                                         Alcaligenes faecalis                                                          Vibrio cholerae                                                               Hemophilus-Bordetella group                                                   Hemophilus influenzae,   H. ducreyi                                                                    H. hemophilus                                                                 H. aegypticus                                                                 H. paraiufluenzae                                    Bordetella pertussis                                                          ______________________________________                                    

Pasteurellae

Pasteurella pestis

Pasteurella tulareusis

Brucellae

Brucella melitensis

Brucella abortus

Brucella suis

Aerobic Spore-forming Bacilli

Bacillus anthracis

Bacillus subtilis

Bacillus megaterium

Bacillus cereus

Anaerobic Spore-forming Bacilli

Clostridium bolulinum

Clostridium tetani

Clostridium perfringens

Clostridium novyi

Clostridium septicum

Clostridium histolyticum

Clostridium tertium

Clostridium bifermentans

Clostridium sporogenes

Mycobacteria

Mycobacterium tuberculosis hominis

Mycobacterium bovis

Mycobacterium avium

Mycobacterium leprae

Mycobacterium paratuberculosis

Actinomycetes (fungus-like bacteria)

Actinomyces israelii

Actinomyces bovis

Actinomyces naeslundii

Nocardia asteroides

Nocardia brasiliensis

The Spirochetes

Treponema pallidum

Treponema pertenue

Treponema carateum

Borrelia recurrentis

Leptospira icterohemorrhagiae

Leptospira canicola

Spirillum minus

Streptobacillus moniliformis

Mycoplasmas

Mycoplasma pneumoniae

Other pathogens

Listeria monocytogenes

Erysipelothrix rhusiopathiae

Streptobacillus moniliformis

Donvania granulomatis

Bartonella bacilliformis

Rickettsiae (bacteria-like parasites)

Rickettsia prowazekii

Rickettsia mooseri

Rickettsia rickettsii

Rickettsia conori

Rickettsia australis

Rickettsia sibiricus

Rickettsia akari

Rickettsia tsutsugamushi

Rickettsia burnettii

Rickettsia quintana

Chlamydia (unclassifiable parasites bacterial/viral) Chlamydia agents(naming uncertain)

    ______________________________________                                        Fungi                                                                         ______________________________________                                        Cryptococcus neoformans                                                       Blastomyces dermatidis                                                        Histoplasma capsulatum                                                        Coccidioides immitis                                                          Paracoccidioides brasiliensis                                                 Candida albicans                                                              Aspergillus fumigatus                                                         Mucor corymbifer (Absidia corymbifera)                                        Rhizopus oryzae                                                               Rhizopus arrhizus            Phycomycetes                                     Rhizopus nigricans                                                            Sporotrichum schenkii                                                         Fonsecaea pedrosoi                                                            Fonsecaea compacta                                                            Fonsecaea dermatitidis                                                        Cladosporium carrionii                                                        Phialophora verrucosa                                                         Aspergillus nidulans                                                          Madurella mycetomi                                                            Madurella grisea                                                              Allescheria boydii                                                            Phialosphora jeanselmei                                                       Microsporum gypseum                                                           Trichophyton mentagrophytes                                                   Keratinomyces ajelloi                                                         Microsporum canis                                                             Trichophyton rubrum                                                           Microsporum andouini                                                          ______________________________________                                    

Viruses Adenoviruses Herpes viruses

Herpes simplex

Varicella (Chicken pox)

Herpes Zoster (Shingles)

Virus B

Cytomegalovirus

Pox Viruses

Variola (smallpox)

Vaccinia

Poxvirus bovis

Paravaccinia

Molluscum contagiosum

Picornaviruses

Poliovirus

Coxsackievirus

Echoviruses

Rhinoviruses

Myxoviruses

Influenza (A, B, and C)

Parainfluenza (1-4)

Mumps Virus

Newcastle Disease Virus

Measles Virus

Rinderpest Virus

Canine Distemper Virus

Respiratory Syncytial Virus

Rubella Virus

Arboviruses

Eastern Equine Eucephalitis Virus

Western Equine Eucephalitis Virus

Sindbis Virus

Chikugunya Virus

Semliki Forest Virus

Mayora Virus

St. Louis Encephalitis Virus

California Encephalitis Virus

Colorado Tick Fever Virus

Yellow Fever Virus

Dengue Virus

Reoviruses

Reovirus Types 1-3

Hepatitis

Hepatitis A Virus

Hepatitis B Virus

Tumor Viruses

Rauscher Leukemia Virus

Gross Virus

Maloney Leukemia Virus

Allergens

The monoepitopic ligand analytes will generally be from about 100 to2,000 molecular weight, more usually from 125 to 1,000 molecular weight.The analytes of interest include drugs, metabolites, pesticides,pollutants, and the like. Included among drugs of interest are thealkaloids. Among the alkaloids are morphine alkaloids, which includesmorphine, codeine, heroin, detromethorphan, their derivatives andmetabolites; cocaine alkaloids, which includes cocaine and benzoylecgonine, their derivatives and metabolites; ergot alkaloids, whichincludes the diethylamide of lysergic acid; steroid alkaloids; iminazoylalkaloids; quinazoline alkaloids; isoquinoline alkaloids; quinolinealkaloids; which includes quinine and quinidine; diterpene alkaloids,their derivatives and metabolites.

The next group of drugs includes steroids, which includes the estrogens,gestrogens, androgens, andrenocortical steroids, bile acids, cardiotonicglycosides and aglycones, which includes digoxin and digoxigenin,saponins and sapogenins, their derivatives and metabolites. Alsoincluded are the steroid mimetic substances, such as diethylstilbestrol.

The next group of drugs is lactams having from 5 to 6 annular members,which include the barbiturates, e.g. phenobarbital and secobarbitaldiphenylhydantoin, and their metabolites.

The next group of drugs is aminoalkylbenzenes, with alkyl of from 2 to 3carbon atoms, which includes the amphetamines, catecholamines, whichincludes ephedrine, L-dopa, epinephrine, narceine, papaverine, theirmetabolites and derivatives.

The next group of drugs is benzheterocyclics which include oxazepam,chlorpromazine, tegretol, imipramine, their derivatives and metabolites,the heterocyclic rings being azepines, diazepines and phenothiazines.

The next group of drugs is purines, which includes theophylline,caffeine, their metabolites and derivatives.

The next group of drugs includes those derived from marijuana, whichincludes cannabinol and tetrahydrocannabinol.

The next group of drugs includes the vitamins such as A, B, C, D, E andK.

The next group of drugs is prostaglandins, which differ by the degreeand sites of hydroxylation and unsaturation.

The next group of drugs is antibiotics, which include penicillin,chloromycetin, actinomycetin, tetracycline, terramycin, theirmetabolites and derivatives.

The next group of drugs is the nucleosides and nucelotides, whichinclude ATP, NAD, FMN, adenosine, guanosine, thymidine, and cytidinewith their appropriate sugar and phosphate substituents.

The next group of drugs is miscellaneous individual drugs which includemethadone, meprobamate, serotonin, meperidine, amitriptyline,nortriptyline, lidocaine, procaineamide, acetylprocaineamide,propanolol, griseofulvin, butyrophenones, antihistamines,anticholinergic drugs, such as atropine, their metabolites andderivatives.

The next group of compounds is amino acids and small peptides whichinclude polyiodothyromines e.g. thyroxine, and triiodothyronine,oxytocin, ACTH, angiotensin, gentamycin, met- and leu-enkephalin theirmetabolites and derivatives.

Metabolites related to diseased states include spermine, galactose,phenylpyruvic acid, and porphyrin type 1.

Among pesticides of interest are polyhalogenated biphenyls, phosphaeeesters, thiophosphates, carbamates, polyhalogenated sulfenamides, theirmetabolites and derivatives.

For receptor analytes, the molecular weights will generally range from10,000 to 2×10⁶, more usually from 10,000 to 10⁶. For immunoglobulins,IgA, IgG, IgE and IgM, the molecular weights will generally vary fromabout 160,000 to about 10⁶. Enzymes will normally range from about10,000 to 600,000 in molecular weight. Natural receptors vary widely,generally being at least about 25,000 molecular weight and may be 10⁶ orhigher molecular weight, including such materials as avidin, thyroxinebinding globulin, thyroxine binding prealbumin, transcortin, etc.

Label Quencher

The quencher molecule is a chromophore which absorbs light in thewavelength band emitted by the chemiluminescer. Preferably, the quencherwill absorb light at a wavelength close to the emission maximumwavelength of the chemiluminescer. What is desired, is that there be ahigh efficiency of energy transfer when the quencher is in relativelyclose juxtaposition to the chemiluminescer source. Normally, thequencher will absorb light at greater than about 350 A, more usually atgreater than about 400 A. Various chromophores which may be employed asquenchers include the xanthene dyes, which include the fluoresceinsderived from 3,6-dihydroxy-9-phenylxanthhydrol and rosamines andrhodamines, derived from 3,6-diamino-9-phenylxanthhydrol. The rhodaminesand fluoresceins have a 9-o-carboxyphenyl group and are derivatives of9-o-carboxyphenylxanthhydrol.

These compounds are commercially available with substituents on thephenyl group which can be used as the site for bonding or as the bondingfunctionality. For example, amino and isothiocyanate substitutedfluorescein compounds are available.

Other dyes which may be used as quenchers include3-phenyl-7-isocyanatocoumarin, acridines, such as9-isothiocyanatoacridine and acridine orange;N-(p-(2-benzoxazolyl)phenyl)maleimide; benzoxadiazoles, such as4-chloro-7-nitrobenzo-2-oxa-1,3-diazole and7-(p-methoxybenzylamino)-4-nitrobenzo-2-oxa-1,3-diazole; stilbenes, suchas 4-dimethylamino-4'-isothiocyanatostilbene and4-dimethylamino-4'-maleimidostilbene; N,N'-dioctadecyloxacarbocyaninep-toluenesulfonate; pyrenes, such as 8-hydroxy-1,3,6-pyrenetrisulfonicacid, and 1-pyrenebutyric acid; merocyanines e.g. merocyanine 540, rosebengal, 2,4-diphenyl-3(2H)-furanone; cyanines; anthiaquinones;porphyrines; triarylmethanes; as well as other readily available dyeswhich are capable of quenching. These dyes, either have activefunctionalities for conjugation or such functionalities may be readilyintroduced.

It should further be noted that the absorption and emissioncharacteristics of the dye may vary from being free in solution andbeing bound to a protein or ligand. Therefore, when referring to thevarious wavelength ranges and characteristics of the dyes, it isintended to indicate the dyes as employed and not the dye which isunconjugated and characteristized in an arbitrary solvent. In the areaof overlap between the chemiluminescer and quencher, it is desirablethat the quencher should have a high transition probability.

Finally, the "blue fluorescent proteins" and/or "green fluorescentproteins" normally associated with certain bacterial luciferases e.g.the luciferase from Photobacterium fisheri, may also be used as aquencher.

Chemiluminescer

The chemiluminescent source may have a single component or a pluralityof components, usually two or three components. While it is feasiblethat there be a single molecule which is thermally labile and ondecomposition chemiluminesces, such as certain dioxetanes, for a numberof reasons the use of these molecules will not be commerciallypractical. While one could prepare reagents and maintain them atsufficiently low temperatures, so that the rate of decomposition wasacceptably slow and then warm the reagent immediately prior to use, suchtechnique will generally be inconvenient, even though it does have someparallel with radioimmunoassay. Therefore, for the most part, thechemiluminescence source will have at least two components and the majorportion of the discussion will be directed to this situation.

For purposes of convenience, the chemiluminescence source will bedivided into two categories: those which do not involve the intermediacyof enzyme catalysis; and those which do involve enzyme catalysis.

Considering chemiluminescence sources which do not involve enzymecatalysis, only those sources can be employed which chemiluminesce underconditions which either do not inhibit the binding of the receptor tothe ligand, or degrade the receptor and ligand at an unacceptable rateduring the period of measurement. While ordinarily chemiluminescentsources which are dependent upon nonaqueous solvents and strong basicconditions, greater than pH11, will not be useful, techniques can beemployed involving rapid injection or flow techniques where themodulated emission is substantially completed before the protein isdenatured and significant disassociation occurs. After injection ofbase, one would observe a burst of light which could be measured.

A diverse number of families of compounds have been found to providechemiluminescence under a variety of conditions. One family of compoundsare 2,3-dihydro-1,4-phthalazinediones. The most popular compound isluminol, which is the 5-amino compound. Other members of the familyinclude the 5-amino-6,7,8-trimethoxy and the dimethylamino[ca]benzanalog. These compounds can be made to luminesce with alkaline hydrogenperoxide or calcium hypochlorite and base. Another family of compoundsare the 2,4,5-triphenylimidazoles, with lophine as the common name forthe parent product. Chemiluminescent analogs include para-dimethylaminoand -methoxy substituents.

The next group of chemiluminescent compounds are indolen-3-ylhydroperoxides, precursors thereto and derivatives thereof.

The next group of compounds are the bis-9,9'-biacridinium salts, ofwhich lucigenin, N,N'-dimethyl-9,9'-biacridinium dinitrate isillustrative. These compounds chemiluminesce upon combination withalkaline hydrogen peroxide.

The next group of compounds are acridinium salts which are substitutedin the 9 position. Particular substituents are carboxylic esters,particularly the aryl esters, acyl substituents, particularly benzoyl,and cyano. Alkaline hydrogen peroxide is employed to inducechemiluminescence.

Another group of compounds are various acyl peroxy esters andhydroperoxides, which may be formed in situ in combination withcompounds such as 9,10-diphenylanthracene.

Another source of chemiluminescence is hydroperoxides e.g. tetralinhydroperoxide in combination with metal complexes, particularlyporphyrins and phthalocyanines, where the metals are iron and zinc.

Preferred systrms are those which provide a satisfactory quantumefficiency of emission from the chemiluminescer at a pH at or below 11,preferably at or below 10, and, furthermore, rely on a catalyst whichmay be conjugated to a member of the immunological pair. Where thesystem does not involve the catalyst, the compound which decomposes withthe emission of light will be conjugated to the member of theimmunological pair. In these circumstances, the number ofchemiluminescent molecules with be limited to those which areconjugated.

The next group of compounds are based on chemiluminescers whichchemiluminescence under enzymatic catalysis. Primarily, there are twogroups of enzymatically catalyzed chemiluminescers. The first group arethose compounds which chemiluminesce in combination with alkalinehydrogen peroxide. By employing a peroxidase e.g. horseradish peroxidaseor catalase, in combination with hydrogen peroxide and thechemiluminescer, chemiluminescence can be achieved. Illustrative systemsinclude 2,3-dihydro-1,4-phthalazinediones.

The second enzymatic source of chemiluminescence is based on luciferinsand their analogs and luciferases.

Labeled Ligand

The ligands may be divided into two categories, haptens which aregenerally from 125 to 5,000 molecular weight, more usually from about125 to 2,000 molecular weight and more particularly from about 125 to1,000 molecular weight and antigens which will generally be not lessthan about 2,000 molecular weight, usually not less than about 5,000molecular weight and when present as part of a cell, virus, chromosomeor the like, may have molecular weights in excess of 10,000,000. For themost part, the antigens of diagnostic interest will generally be lessthan about 1,000,000 molecular weight, more usually less than about600,000 molecular weight and more particularly will range from about10,000 to 350,000 molecular weight.

The label will either be a quencher, which will generally be from about125 to 1,000 molecular weight or a component of the chemiluminescentsource, which may be a small molecule of from about 125 to 1,000molecular weight or a large molecule, such as an enzyme or hemin whichwill range from about 10,000 to 250,000 molecular weight, more usuallyfrom about 10,000 to 150,000 molecular weight.

Depending upon the nature of the ligand and the label, the character ofthe labeled ligand will vary widely. The first labeled ligand which willbe considered is the quencher-hapten reagent. Since both molecules aresmall, there will normally be a 1 to 1 ratio with a relatively shortlinking group between the two parts of the quencher-hapten.

Where an antigen is involved, there may be one or more quenchersconjugated to the antigen. Generally, there will be at least about onequencher molecule per 100,000 molecular weight, more usually at leastabout one quencher molecule per 50,000 molecular weight and generallynot more than about one quencher molecule per 1,000 molecular weight,more usually not more than about one quencher molecule per 2,000molecular weight. With antigens in the range of about 10,000 to 300,000molecular weight, the number of quencher molecules will generally be inthe range of about 2 to 30, more usually from about 2 to 20, andpreferably from about 2 to 16.

Where the component of the chemiluminescent source which is conjugatedis a small molecule, that is having a molecular weight in the range ofabout 125 to 1,000, there will normally be a one to one ratio ofchemiluminescer component to hapten in the chemiluminescer-haptenreagent. With antigens, the number of small chemiluminescent componentswill generally be not less than 1, usually not less than 1 per 100,000molecular weight, more usually not less than 1 per 50,000 molecularweight and generally not more than 1 per 1,000 molecular weight, moreusually not more than 1 per 2,000 molecular weight.

Where antigens and large (over 10,000) chemiluminescent sourcecomponents are involved, the ratios will vary widely, with either aplurality of the chemiluminescent source component bonded to theantigenic ligand or a plurality of ligands bonded to thechemiluminescent source component. Generally, the ratio of antigen tochemiluminescent source component will be in the range of about 0.05 to20, more usually in the range of about 0.01 to 10, where both thechemiluminescent source and the antigen have molecular weights in therange of about 10,000 to 300,000.

The nature of the linking group will vary widely depending upon theparticular materials which are being joined. Generally, linking groupswill vary from a bond to about 20 atoms in the chain which are carbon,oxygen, nitrogen and sulfur, particularly carbon, oxygen and nitrogenwhere the nitrogen is substituted solely with carbon or is neutral,where it may be substituted with both carbon and hydrogen e.g. amido. Awide variety of linking groups are set forth in U.S. Pat. No. 3,817,837,which disclosure is incorporated herein by reference.

Where a poly(ligand analog)-label is involved, a hub nucleus may beemployed, which is normally a water soluble polymer and conveniently apoly(amino acid) or polysaccharide.

Usually, the hub nucleus will be from about 25,000 to 600,000 molecularweight, more usually from about 30,000 to 300,000 molecular weight.Enzymes to which ligand analog may be linked will generally vary fromabout 15,000 to 300,000 molecular weight. The same linking groups asdiscussed above may be employed for linking the label and the ligandanalog to the hub nucleus or enzyme.

The functionalities involved in the linking will normally includealkylamine, amide, amidine, thioamide, urea, thiourea and guanidine.Illustrative functionalities involved in linking are carboxylic acids inconjuction with diimides, mixed anhydrides with carbonate monoesters,aldehydes in conjunction with reductants e.g. borohydrides, imidoesters,active carboxylic esters e.g. N-hydroxy succinimide or p-nitrophenyl,isocyanates, isothiocyanates, active halide and the like.

Labeled Receptor

The receptor may be labeled with either the quencher or thechemiluminescent source component. Where the label is a small moleculeof about 125 to 1,000 molecular weight, there will usually be at leastone label per receptor and not more than about one per 1,500 permolecular weight of receptor more usually not more than about one labelper 2,500 molecular weight of receptor and preferably not more thanabout one label per 5,000 molecular weight of receptor. Where thereceptor is an antibody, IgG, the number of labels will generally befrom about 2 to 20, more usually from about 2 to 12. Where the label isa macromolecule, that is of from about 10,000 to 300,000 molecularweight, there will generally be from about 1 to 10 labels, more usuallyfrom about 1 to 6 labels.

The manner of conjugation to the receptor has been indicated previously.

Kits

In carrying out the subject assays, in order to obtain reproducibleresults, it is desirable that the critical reagents be provided inpredetermined ratios, so as to optimize the sensitivity of the assay. Inthe assay for ligand, the critical reagents include labeled ligand,including poly(ligand analog)-label and labeled receptor. In the assayfor receptor, ligand may also be a critical reagent. Besides the desireto have the critical reagents in predetermined proportions, it isfrequently desirable that ancillary materials, such as buffer,stabilizers and the like, be included with critical reagents, so thatdry powders or concentrates may be diluted to form assay solutionsdirectly, avoiding the necessity of weighing the various materials.

In the kit, the reagents will be provided in relative proportions, so asto substantially optimize the sensitivity of the assay to theconcentration range of interest. In addition, included with one or bothof the reagents may be buffer, inert proteins, such albumins,stabilizers, such as sodium azide and the like. Desirably, the reagentsare provided as dry powders, particularly with labeled polyepitopicligand and receptors, where these materials may be lyophilized.

The following examples are offered by way of illustration and not by wayof limitation.

EXPERIMENTAL

All temperatures not otherwise indicated are in centigrade. All percentsor parts not otherwise indicated are by weight except for mixtures ofligands which are by volume.

EXAMPLE 1 Conjugation of horseradish peroxidase to human gamma-globulin(hIgG)

The method employed is described in Nakane and Kawaoi, J. Hist. Cyto. 22(12), 1084-1091 (1974).

In 1 ml of 0.3 M sodium bicarbonate buffer, pH 8.1, was introduced 6 mghorseradish peroxidase (HRP) and 100 μl of a 1% aqueous solution of2,4-dinitro-1-fluorobenzene and the mixture incubated for 1 hr. Themixture was then dialzyed against 0.01 M sodium carbonate, pH 9.5 for 2hrs followed by dialysis against 0.3 M sodium bicarbonate buffer, pH8.1.

An approximately 1.5 ml solution of the HRP material prepared above wasadded to 1 ml 0.4 M sodium periodate and the mixture allowed to standfor 45 min at room temperature. To the solution was then added 25 μl of0.32 M aqueous ethylene glycol, the mixture allowed to stand for 1 hr,followed by dialysis for 2 hrs in a collodion bag apparatus against 0.01Msodium carbonate, pH 9.5. The residue in the dialysis bag was thencombinedwith 5 mg hIgG and the mixture allowed to stand for 1 hr. Atthis time, 15 mg sodium borohydride was added, the mixture allowed tostand for 1.25 hrsat room temperature and the product then dialyzedovernight in a collodion bag apparatus against PBS, pH 7. The residue inthe dialysis bag was then chromatographed on Sephadex G-200 with 0.01 MPBS, pH 7. Fractions were collected, with fraction 7spectrophotometrically found to be 2.5×10.sup. -7 M hIgG and 4.95×10⁻⁷ MHRP.

EXAMPLE 2 Conjugation of fluorescein to anti(hIgG)

Into a vial fitted with stirring bar was introduced 5 mg lyophilizedrabbitanti(hIgG) (Miles Laboratories, Lot 18, Code 64-155) and themixture dissolved in 0.5 ml aqueous sodium phosphate, pH 8.0 and the pHadjusted to 9 with aqueous sodium carbonate buffer. A solution of 0.3 mgfluorescein isothiocyanate in 0.3 ml DMF was added over about 40 secswithvigorous stirring and the mixture stirred for 60 min. At the end ofthis time, the reaction mixture was chromotographed on a Sephadex (G-25)columnand the fractions collected. A fraction was obtained having 2.4mg/ml of anti(hIgG) with a fluorescein/anti(hIgG) ratio of about 5 to 1.

In order to demonstrate the subject invention, the following assay wascarried out at room temperature. The solutions employed were a 1.86mg/ml aqueous solution of hIgG, a 0.023 mg/ml solution of thefluorescein-anti(hIgG) conjugate (prepared above) and a 2.5×10⁻⁸ Msolution of the HRP-hIgG conjugate. In addition, 100 μl each of aqueoussolutions 10⁻³ M luminol and 10⁻⁵ M hydrogen peroxide were also added.The following table indicates the amounts of materials added and theresults as read as counts per 0.1 min at different times from the timeof mixing.

                  TABLE                                                           ______________________________________                                                                  Counts per 6 sec from                                      Fluorescein-                                                                             HRP-    time of mixing in min.                              hIgG   anti(hIgG) hIgG    (in thousands)                                      μ1  μ1      μ1   5      15     60                                    ______________________________________                                        0      0          25      23.3   38.3   56.8                                  1      5          25      27.2   41.1   60.8                                  2.5    5          25      34.9   50.3   71.3                                  5      5          25      36.8   44.7   81.7                                  10     5          25      49.8   66.0   78.9                                  ______________________________________                                    

The apparatus employed was a β-Mate Scintillation Counter,non-coincidence mode.

It is evident from the above results, that a standard curve can bepreparedfor determining the amount of an analyte in an assay medium. Themethod is quite simple in that the reagents may be rapidly combined anda reading taken within a very short period of time. In addition, afterabout 0.5 hour the readings stabilize, so that the timing of the readingbecomes less critical.

The subject assay provides a convenient means for determiningquantitatively a wide variety of analytes. In addition, the methodallows for multiplication of the signal, by employing a catalyticsystem, either enzymatic or nonenzymatic, which provides a plurality ofevents for each molecule of analyte present in the medium. In addition,the method avoids the problems of light scatter and protein absorptionand emission interfering with the results which are determined.

Although the foregoing invention has been described in some detail byway of illustration and example for purposes of clarity ofunderstanding, it will be obvious that certain changes and modificationsmay be practiced within the scope of the appended claims.

What is claimed is:
 1. A diagnostic kit for use in a method fordetermining in an assay solution, the presence of an analyte in a samplesuspected of containing said analyte, said analyte being a member of animmunological pair consisting of ligand and antiligand, said ligandhaving at least one epitopic site and said antiligand being capable ofspecifically binding to said epitopic site of said ligand; wherein alight emitting reciprocal pair are employed as labels, said lightemitting reciprocal pair consisting of a chemiluminescence source havingat least one component and a quencher capable of quenching the lightemitted by said chemiluminescence source without collision, said labelsbeing conjugated to members of said immunological pair to form achemiluminescence label conjugate and a quencher label conjugate, andwherein in said assay solution the amount of quencher brought withinquenching distance of said chemiluminescence source is related to theamount of analyte in said assay medium; said kit comprising in relativeamount to substantially optimize said method, said chemiluminescencelabel conjugate and said quencher labeled conjugate.
 2. A kit accordingto claim 1, wherein said chemiluminescence source component is anenzyme.
 3. A kit according to claim 2, wherein said enzyme is conjugatedto said ligand.
 4. A kit according to claim 1, wherein saidchemiluminescence source component and said quencher dye are bothconjugated to antiligand.